Carbohydrates 1b (gluconeogenesis)

Question 1

Which cells rely on glucose as their main source of energy?

Answer 1

Brain cells, RBC’s, nervous system, testis, embryonic tissue

Question 2

How many out of the 10 glycolysis reactions are irreversible?

Answer 2

3

Question 3

What are the 4 reactions called that side step the three irreversible reactions of glycolysis

Answer 3

Bypass reactions, allow for the independant control of pathways and to stop them canceling each other out

Question 4

Where do the first two bypass reactions occur?

Answer 4

Mitochondria

Question 5

What are the first two bypass reactions?

Answer 5

Pyruvate - Oxaloacetate
Oxaloacetate - PEP
Pyruvate can be derived from lactate, Lactate +(NAD)+ (lactate dehydrogenase) = pyruvate + NADH

Question 6

What is the pathway of molecules in the first bypass reactions if pyruvate has and hasn’t been derived from Lactate?

Answer 6

Lactate : Lactate, Pyruvate, Oxaloacetate, PEP
No Lactate: Pyruvate, Oxaloacetate, Malate, Oxaloacetate, PEP

Question 7

What is the control point for gluconeogenesis?

Answer 7

The third bypass reaction for, it is irreversible under cell conditions

Question 8

What enzyme catalyses the hydrolysis of f-1,6-bisP to Fructose-6-Phosphate?

Answer 8

Fructose 1,6-bisphosphatase

Question 9

What is the fourth bypass reaction?

Answer 9

Dephosphorylation of G-6-P to glucose, the final stage in gluconeogenesis. Glucose 6-phosphatase is the catalyst

Question 10

Why is G-6-P normally the end point for gluconeogenesis?

Answer 10

Allows the cells to ‘trap’ the glucose in glycogen complexes

Question 11

Where does the final step of gluconeogeneogenesis to make free glucose take place?

Answer 11

Lumen of the ER

Question 12

Where is most fructose metabolised?

Answer 12

Liver

Question 13

How many ATP are used for each molecule of Frutose converted into Glyceraldehyde -3- phosphate?

Answer 13

1

Question 14

What is the first molecule of ATP used for?

Answer 14

Converts fructose to fructose - 1 - Phosphate (using fructokinase enzyme)

Question 15

What is the reaction pathway for fructose-1-phosphate?

Answer 15

Reacts with fructose-1-phosphate aldolase froming glyceraldehyde and dihydroxyacetone phosphate. Glyceraldehyde reacts with triose kinase and another molecule of ATP to form Glyceraldehyde 3-Phosphate

Question 16

How is galactose converted to glucose 1-phosphate?

Answer 16

Through use of sugar-nucleotide derivative UDP-galactose

Question 17

What is the function of the pentose phosphate pathway?

Answer 17

Produces NADPH for all organisms, produces pentose sugars, metabolises the small amount of pentoses in the diet (usually come from digestion of nucleotides)

Question 18

What is the oxidative irreversible part of the pentose phosphate pathway?

Answer 18

Generates NADPH
Converts G-6-P to pentose phosphate
Required when lots of NADPH is needed

Question 19

What is the reversible non-oxidative part?

Answer 19

Interconverts G-6-P and pentose phosphate to produce lots of different 3,4,5,6,7 carbon sugars
When lots of nucleotides are required

Question 20

What is the function of NADPH?

Answer 20

Links anabolic and catabolic pathways

Question 21

What type of reaction is NAD+ involved in?

Answer 21

Metabolism of dietary sugars in the redox reactions of glycolysis and the citric acid cycle

Question 22

What type of reactions is NADP+ involved in?

Answer 22

Anabolism to convert simple precursors into things like fatty acids
Also acts as an antioxidant

Question 23

What stops NADP+ being used in metabolism?

Answer 23

Enzyme specificity

Question 24

What is the effect of being drunk on gluconeogenesis?

Answer 24

Reduced gluconeogenesis

Question 25

How can being drunk be linked to lacticacidaemia?

Answer 25

Reduced level of NAD+
Less lactate converted into pyruvate

Question 26

How can being drunk be linked to hypoglycemia?

Answer 26

Decreased blood glucose concentration since gluconeogenesis is inhibited